A quick question about Stun Pulse attachment

If I put Stun Pulse on Shock Gloves, does it give me Stun 5 or Stun 3 and Stun 2 (before modding)?

You may not even be able to mod it, depending on the GM, since it mod is intended for weapons that do not already provide stun damage. Either way, no it would not stack with any inherent stun quality since the mod itself provides a stun quality of 2, not +2.